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Supporting Information
for
Angew. Chem. Int. Ed. Z 54150
© Wiley-VCH 2004
69451 Weinheim, Germany
1
A Multiproperty Switching Molecular Array
based on the Redox Behavior of a Ferrocenyl
Polychlorotriphenylmethyl Radical
Christian Sporer, Imma Ratera, Daniel Ruiz-Molina,
Yuxia Zhao, José Vidal-Gancedo, Klaus Wurst, Peter
Jaitner, Koen Clays, André Persoons, Concepció
Rovira, Jaume Veciana*
Professor Jaume Veciana
Institut de Ciència de Materials de Barcelona
(CSIC)
Campus Universitari, 08193—Bellaterra, Spain
Tel: +34 3 93 580 1853
Fax: +34 3 93 580 5729
E-mail: vecianaj@icmab.es
CH2-PClClClClClClClClClClClClClClHOEtOEtO18-crown-6KOH (s)1H231[1+]BF4-2 equiv Ag BF41equiv Ag BF4ClClClClClClClClClClClClClClFeHOFeK+(18-crown-6)[1-]
Chart S1. Synthesis of radical 1 and salts K+(18-crown-
6)[1-] and [1+]BF4-.
2
Experimental Section
1. General procedures:
All solvents were reagent grade from SDS and were used as
received and distilled otherwise indicated. All reagents,
organic and inorganic, were of high purity grade and
obtained from E. Merck, Fluka Chemie and Aldrich Chemical
Co. Elemental analyses were obtained in the Servei de
Microanalisi del CID (CSIC), Barcelona.
UV–Vis and NIR spectra were recorded using a Varian Cary
05E spectrophotometer. Infrared spectra were recorded on a
FT-IR Perkin Elmer and 1H-NMR spectra on a Bruker AC250
spectrometer. Fluorescence measurements where performed in
CH2Cl2 with a KONTRON SFM-25 spectrofluorimeter
Hyper-Rayleigh scattering experiments were carried out with
the compounds dissolved in CH2Cl2, which was previously
saturated with nitrogen and passed through 0.2 mm filters.
To avoid decomposition of the compounds, all solution were
protected against light with an aluminium foil. Crystal
Violet chloride (b = 338·10-30 esu, in CH3OH) was used as
external reference and standard local field correction
factors were applied [((nD_ + 2)/3)3, where n is the
refractive index of the solvent at the sodium D line]. A
relative error of 5% is estimated due to the high laser
stability.
Cyclic voltammograms were recorded with the conventional
three-electrode configuration in CH2Cl2 containing 0.1MnBu4N+PF6
-, as supporting electrolyte, with Pt-electrodes and
a Ag/AgCl electrode as the reference one. Resulting
potentials were corrected vs. the fc/fc+ couple (+470 mV,
see: N. G. Connelly, W.E. Geiger, Chem. Rev. 1996, 96, 877-910).
Chronoamperometric experiments were performed with an
electrochemistry equipment from EG&G Princeton Applied
3
Research, using a platinum wire as working electrode and a
Ag/AgCl electrode as the reference electrode. Anhydrous
CH2Cl2 was freshly distilled over P2O5 under nitrogen.
Anhydrous THF was freshly distilled over Sodium under
Nitrogen. 0.1M Tetrabutylammonium hexafluorophosphate was
used as the supporting electrolyte.
EPR spectra were obtained on a Bruker ESP-300E spectrometer
operating at X-band (9.3 GHz), equipped with a rectangular
cavity T 102. Spectra were recorded in the 4 - 300 K range
using a Bruker variable-temperature unit and an Oxford
Instruments EPR-900 cryostat. The signal-to-noise ratio was
increased by accumulation of scans using the F/F lock
accessory Bruker ER 033M and a NMR gaussmeter Bruker ER
035M, to guarantee a high-field reproducibility.
Precautions to avoid undesirable spectral line broadening
such as that arising from microwave power saturation and
magnetic field over-modulation were taken.
2. Crystal structure of radical 1:
X-ray structure analysis of C40H29Cl14Fe, Mr = 1061.78; brown
plates with the dimensions 0.25 x 0.06 x 0.03 mm;
triclinic, space group P-1 (no.2), a = 9.1198(8), b =
15.805(2), c = 17.310(2) pm , a = 116.150(5), b =
95.495(7), g = 99.661(7)deg, V = 2166.9(4) nm3, rcalcd = 1.627
gcm-3, Z = 2, T = 233(2) K, l(MoK_) = 0.71703. Data were
measured with a Nonius Kappa CCD, intensities were
integrated with DENZO and scaled with SCALEPACK; 6943
measured reflections, of which 3738 with I>2s(I) were
included in the structure refinement against F2 (SHELXL
97). The structure was solved by direct methods (SHELXS
97); heavy atoms with anisotropic temperature factors
except C1 to C12 which were refined isotropically; hydrogen
atoms were calculated. The ethylene bridge C11-C12 display
an orientation disorder (1:1). Refinement with 449
variables with a GOF of 1.072. Final R-values for 2538
4
reflections with I>2s(I): R1 = 0.0878 (against F2) and wR2
= 0.1615 (against F). Crystallographic data (excluding
structure factors) for the structure reported in this paper
have been deposited with the Cambridge Crystallographic
Data Centre, CCDC-191558. Copies of this information may be
obtained free of charge from The Director, CCDC, 12 Union
Road, Cambridge CB2 1EZ, UK (Fax: +44-1223-336033; email:
deposit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk.
Program for crystal structure solutions, Göttingen
(Germany), 1997; G. M. Sheldrick, SHELXS-97.
3. Preparation of compound 1H:
Phosphonate 2 (637 mg, 0.726 mmol) was suspended in dry THF
(20mL) under argon. The solution was cooled down to -78°C
and potassium-tert-butoxide (190 mg, 1.69 mmol) was added.
The orange-yellow ylide suspension that was formed
immediately was stirred for 15 min after which the
temperature was increased to 0°C by means of an ice bath
and finally the nonamethylferrocenecarboxaldehyde 3 (271
mg, 0.800 mmol), dissolved in THF (5 mL) was added dropwise
to the reaction mixture. Stirring was continued for 60
hours at room temperature after which the reaction mixture
was quenched with HCL (5 mL, 2N) and extracted with
chloroform (4 portions of 25 mL). The organic layer was
washed with water (20 mL), dried over sodium sulfate and
evaporated under reduced pressure. Chromatographic workup
(silica, hexane/ether, 1/1) yielded 700 mg (90%) of pure
1H. Characterization Data: Elemental Anal. Calc. for
C40H30Cl14Fe__C6H14: C, 46.7; H, 3.37; Found C, 46.52; H,
3.43; Cyclic Voltammetry in CH2Cl2 and 0.1M
tetrabutylammonium hexafluorophosphate as electrolyte: E_ =
0.090 V vs. Ag/AgCl; FT-IR (KBr, n in cm-1): 2954; 2923;
2854; 1624;; 1536; 1451; 1423; 1373; 1299; 1241; 1135;
1028; 972; 809; 716; 683; 648; 529; 468; UV-Vis-NIR
(CH2Cl2, lmax in nm (e)): 338 (12100); 519 (2200); EM-LDI-TOF
5
(negative mode): m/z (amu/e-) 1063, [M+1H]-; 1028 [M-1Cl]-
; 992 [M-2Cl]-; 957; 870; 822; 679; 481; 311; NMR (CDCl3):1H: d 7.01 (1H, s, CH), 6.92 (1H, d, J = 16.6Hz, CH=CH),
6.65 (1H, d, J = 16.6Hz, CH=CH), 1.90 (6H, s, CH3), 1.75
6H, s, CH3), 1.65 (15H, s, CH3).
4. Preparation of salt K+(18-crown-6)[1]-:
Compound 1H (350 mg, 330 _mol) was dissolved in dry THF (10
mL) under argon. 18-Crown-6 (100 mg, 375 mmol) and finely
grinded powder of potassium hydroxide (200 mg, 3.60 mmol)
were added to the solution which was left with strong
stirring for 24 hours. The solution was filtered and the
solvent was reduced in volume to approximately 1 mL. The
product precipitated on addition of dry n-hexane. It was
filtered, redissolved in a few mL of dry CH2Cl2 and
reprecipitated with dry n-hexane two times more. Yield: 400
mg (89%) of K+(18-crown-6)[1]- as a dark violet powder.
Characterization Data: Elemental Anal. Calc. for
C52H53O6Cl14KFe: C, 45.75; H, 3.91; Found C, 45.6; H, 3.75;
FT-IR (KBr, n in cm-1): 2913; 2857; 1631; 1472; 1453; 1373;
1352; 1335; 1283; 1249; 1107; 962; 838; 721; 663; 687; 649;
612; 584; 530; 523; UV-Vis-NIR (CH2Cl2, lmax in nm (e)): 534
(31350); (THF, lmax in nm (e)):534 (31300); EM-LDI-TOF
(negative mode): m/z (amu/e-) 1061, [M(1-)]; 1026, [M-
1Cl]-; 991, [M-2Cl]-; 956, [M-3Cl]-; 303.
5. Preparation of radical 1:
The K+(18-crown-6)[1]- salt [200 mg, 146 _mol] was
dissolved in dry CH2Cl2 (5 mL) and solid AgBF4 (30 mg, 150
mmol) was added. After a few minutes the color of the
solution changed form violet to dark-brown and grey
precipitate of metallic silver was formed. The solution was
left with strong stirring for 30min after which it was
6
filtered and evaporated. The product was redissolved in dry
n-hexane, filtered again and the solvent was evaporated
under reduced pressure. Yield: 108 mg (70%) of radical 1 as
dark brown power. Characterization Data: Elemental Anal.
Calc. for C40H29Cl14Fe: C, 45.24; H, 2.75; Found C, 45.5 ; H,
2.85. FT-IR (KBr, n in cm-1): 2901; 1612; 1505, 1474; 1420;
1375; 1351; 1335; 1262; 1108; 1084; 1029; 965; 838; 816;
736; 712; 667; 652; 530; UV-Vis-NIR (CH2Cl2, lmax in nm (e)):
346 (16900), 385 (23950), 497 (8000), 656 (3900), 1520
(1600); (THF, lmax in nm (e)): 346 (15250), 385 (22800), 497
(8600), 656 (4400), 1540 (1700). EPR (THF at 300K), giso =
2.0024; a(1H) = 1.6 G; DH1/2 = 1.4 G. EPR (in frozen THF at
77 K), g^ = 2.0022; g// = 2.0075. EM-LDI-TOF (positive
mode): m/z (amu/e-) 1061, [M]-; 991, [M-2Cl]-; 956, [M-3Cl]-
; 371; 303; 287; 242; 215; Cyclic voltammetry in CH2Cl2 and
0.1 M tetrabutylammonium hexafluorophosphate as
electrolyte: (1/1-): E_ = -238 mV, (1/1+): E_ = +86 mV,
(1+/1++): E_ = aprox. 1800 mV vs Ag/AgCl, corrected vs
fc/fc+ couple.
6. Preparation of salt [1]+BF4-:
salt K+(18-crown-6)[1]- (90 mg, 66 _mol) was dissolved in
CH2Cl2 (5 mL) and AgBF4 (27 mg, 137 _mol) was added. After a
few minutes the color of the solution changed form violet
to dark-yellow-brownish and a grey precipitate of metallic
silver was formed. The solution was left with strong
stirring for 30min after which it was filtered and reduced
in volume to approximately 1mL. On addition of dry n-hexane
small white needles appeared floating on the surface and
them they were sucked off. On further addition of n-hexane
the a brown powder precipitated which as filtered,
redissolved in a few mL of dry CH2Cl2 and then treated two
times with dry n-hexane the same way as described before.
Yield: 60 mg (79%) of salt [1]+BF4- as a dark brown powder.
Characterization Data: Elemental Anal. calc. for
7
C40H29BCl14F4Fe: C, 41.83; H, 2.54; Found C, 42.3 ; H, 2.65 .
FT-IR (KBr, n in cm-1): 2956; 2921; 2855; 1628; 1474, 1383;
1336; 1259; 1056; 816; 710; EPR (THF at 300K), giso =
2.0024. EPR (in toluene/CH2Cl2 1:1, at 4 K), g// = 4.03; g^ =
1.65; ÁD’Á = 155 G; ÁE’Á = 35 G. UV-Vis-NIR (CH2Cl2, lmax in
nm (e)): 285 (33300), 324 (27300),385 (36650), 425 (s,
15800), 565 (2050), 805 (850); (THF, lmax in nm (e)): 285
(26450), 324 (21950), 385 (27750), 425 (s, 20800), 565
(1650), 804 (750).
Non linear optical properties of 1, 1+, and 1-:
The b(800) values for 1, 1+, and 1- are resonantly enhanced
to a certain extent due to the closeness of the second
harmonic wavelength of the excitation laser to an
absorption band. Unfortunately, determination of static
hyperpolarizability values b(0) using the simple two-level
model is not straightforward for organometallic compounds
since several charge transfer excitations may contribute to
the observed b value. Furthermore, as it was recently
pointed out, the two-level model is also inappropriate for
open-shell molecules [1] and results in underestimated
values for the static hyperpolarizability. To evaluate the
influence of fluorescence in the nonlinear optical
responses of the studied compounds, emission spectra when
irradiated at a wavelength of 375 nm were recorded. No
studied compounds show any emission at 400 nm, thus the
contribution of fluorescence to the HRS signal is shown to
be zero. In summary, it can be said that radical 1 gives an
intense nonlinear optical response while this response is
much lower in its reduced or oxidized forms.
EPR studies:
The two paramagnetic compounds show difference in the
magnetic properties in solution studied by EPR spectroscopy
8
So, 1 exhibits at 300 K two main, symmetrical, partially
overlapped lines, centered at g = 2.0024, that are caused
by the hyperfine coupling with one H atom of the ethylene
bridge with a(H) = 1.6 G; as occurs for other vinyl
substituted radicals of this family. [10] By contrast, 1+
displays under similar conditions an asymmetrical
structured line at g = 2.0024. Spectral differences of
these two open-shell species increase progressively by
lowering the temperature becoming entirely different at
very low temperatures. Thus, 1 shows at 4 K the typical
spectrum of an organic radical with a very small magnetic
anisotropy, gÁÁ = 2.0075 and g^ = 2.0022, while 1+ exhibits
the characteristic fine structure of a triplet species with
zero-field splitting parameters of ÍD’Í = 155 Gauss and ÍE’Í
= 35 Gauss with principal components of g-tensor being gÁÁ =
4.03 and g^ = 1.65.
[1] S. diBella, I. Fragala, T. J. Marks, M. A. Ratner, J.
Am. Chem. Soc. 1996, 118, 12747-12751.
9
Figure S1. Crystal structure of 1. Thermal ellipsoids are
shown at the 30% probability level.
10
400 600 800 1000 1200
0.0
0.2
0.4
0.6
0.8
1.0534 nm385 nm
absorbance
wavelength / nm
400 600 800 1000 1200
0.0
0.2
0.4
0.6
0.8
1.0
385 nm
absorbance
wavelength / nmFigure S2 Spectroelectrochemical experiments showing the
evolution of UV-Vis-NIR spectra during the oxidation of 1-
(top) and of radical 1 (bottom) in CH2Cl2. Trends of
intensity changes are shown for a few particular bands with
arrows pointing up and down.
800 1200 1600 2000
0.000
0.025
0.050
0.075
0.100
0.125
805 nm
1520 nm
800 1200 1600 2000
0.000
0.025
0.050
0.075
0.100
0.125
1520 nm
11
relativepotential / V
+0.5
0
-0.5
1 2 3 4 5 6 7 8 9 10 11 12 Oxidation / Reduction steps
1+
1
1-
1 2 3 4 5 6 7 8 9 10 11 120
5
10
15
20
25
30
35
1
1+
1-
e / 103 M-1cm-1
1 2 3 4 5 6 7 8 9 10 11 125
10
15
20
25
30
1-
1
1+
e / 103 M-1cm-1
12
Figure S3. Cyclic stepwise oxidations and reductions
carried out in THF with a chronoamperometric technique
following the changes by visible spectrometry. Top: Changes
observed at a wavelength of 385 nm where 1 (�) and 1+ (p)
exhibit the strongest absorption and 1- (¢) shows a very
weak abosrption. Bottom: Changes observed at 534 nm where 1(�) and 1+ (p) exhibit very weak absorptions while it is
maximum for 1- (¢). Middle: Fixed potentials used in the
different steps of cyclic redox experiments.
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